The two men, whom the source declined to identify, are in addition to James Lohr, 47, and Thomas Guolee, 31, two men the El Paso County Sheriff's Office asked police to be on the lookout for on Wednesday. One or both could be headed toward Nevada, the office said.

Police want to question Lohr and Guolee -- whom police described as associates of the white supremacist 211 Crew gang -- in relation to the death of state prisons chief Tom Clements. The man suspected of killing Clements, Evan Ebel, also had been a 211 Crew member. He died in a shootout with Texas deputies.

The other two men, brought in for questioning in recent days by El Paso County authorities, are also 211 Crew members, the source said. Both associated with Ebel in the days before Clements' death, the source said, and at least one is a parolee.

He had been sentenced to eight years in prison in 2005 for armed robbery. In 2008, he was sentenced to another four years -- to be served consecutively -- for punching a prison guard.

Two days after Clements was killed, Ebel died in northern Texas in a gun battle with authorities that left a sheriff's deputy wounded.

Kramer said Lohr and Guolee may also pose a threat to the safety of officers who encounter them.

Police have little to go on in order to track them.

"We don't have vehicle information," Kramer said. "We don't have a concerted search out looking for them. We don't know their whereabouts." Lohr has multiple misdemeanor warrants for his arrest unrelated to the Clements case.

Guolee has a felony warrant for his arrest, also unrelated to the Clements case.